Synthesis and Characterization of Halide Perovskites and Lower-Dimensional Metal Halide Based Materials

The goal of this doctoral thesis is to synthesize metal halide octahedra based materials of varying dimensionality and explore their intrinsic structure-property relationships while attempting to apply them in prototype devices. In Chapter 2 we found using our solvent acidolysis crystallization (SAC) method, 44% of methylammonium can be replaced with a larger organic cation (dimethylammonium) without breaking the 3-dimensional (3D) perovskite structure. We then employed different temperature-dependent studies to explore the implications of such a mixed organic cation composition on the structure and on the optoelectronic properties as well as on photodetector performance. In Chapter 3 we used the SAC process to fabricate lead-free 2D methylammonium copper halide materials. Here we found that tuning the halide compositions not only modulated the bulk phase and optical properties but also the finer structural effects such as vacancy positions and thermal disorder parameters. We connected these local atomic scale observations to the efficacy of ionic migration in these materials that also modulates their performance in resistive switching memory devices. In Chapter 4 we explored the structural versatility of Cs-Pb-Br based compounds by studying the connection between the nature and size of the solvated species and the precipitated 0D Cs4PbBr6 and 3D CsPbBr3 powders. Identifying the spectroscopic signatures of the species helped us select the appropriate solvents to obtain 3D-free Cs4PbBr6 that we studied for the first time using 133Cs and 207Pb solid-state nuclear magnetic resonance. We hypothesized on the possible origins of the green emission in these 0D compounds and also studied their suitability for radioluminescence applications.